1. Field of the Invention
The subject invention pertains to the field of electric motive power systems. More particularly, the invention pertains to oscillating motors with energizing winding circuit control.
2. Description of the Prior Art
In rotary solenoids electrical energization of a winding produces oscillating movement of a shaft. In certain prior art rotary solenoids magnetic attraction generated by energization of the winding attracts an armature to move the shaft in one direction and tensions a coil spring which moves the shaft in the other direction when the winding is deenergized. In this type of prior art rotary solenoids it is difficult to provide equal torque in both directions since electromagnetism is the motive power in one direction and resilient energy is the motive power in the other direction. This type of rotary solenoid is subject to failure if the spring breaks and becomes ineffective if the spring weakens. These problems are avoided by another type of prior art rotary solenoid which utilizes a separate winding for each direction of movement. However, the use of two windings results in a structure which is relatively heavy, bulky, and expensive in relation to the single winding, spring returned type. Both of these types of rotary solenoid are subject to improper operation when a circuit for energizing a winding fails, and the direction of movement on such failure is unpredictable since the circuit may fail either on or off.
In solenoid operated devices where great reliability is required, it is known to use a direct current energizing circuit which outputs a predetermined number of alternate positive and negative pulses. This arrangement is effective since it is unlikely that any single energizing circuit failure will produce this number of such pulses. It is apparent that neither of the above types of prior art rotary solenoid is suited for use with such an energizing circuit.
It is often desireable to maintain the shaft of a rotary solenoid in the extreme positions of its oscillating movement. In prior art solenoids the necessary detent action for this purpose is obtained either by mechanical elements, which requires greater weight and expense, or by maintaining electrical energization of the winding which requires a continuous power drain and cannot be used to maintain the shaft in a position to which it is urged by a spring.
Polarized relays, in which different switching functions occur on application of opposite polarity direct current to a winding, are well-known. It is also known to utilize direct current polarized actuation where great reliability is required, as in certain signaling applications. However, insofar as is known to the applicant, prior art polarized devices for these purposes are not suited for a use as a rotary solenoid, particularly where a relatively high torque, compact, efficient, and rugged actuator is required.